Human platelet derived growth factor (PDGF) is composed of a dimer of two homologous polypeptide chains designated A and B. There are 3 dimeric forms AA, AB, and BB, the AB form being the predominant form found in serum, originating from the alpha granule of platelets. A number of tumor cells have been shown to express AA or BB homodimers. Glioma cells express the AA dimer (Nister et al, Cell, 52, 791-799 (1988)), as do osteosarcoma cells (Betsholtz et al, Nature, 320, 695-699). B chain expression is elevated in human atherosclerotic lesions (Barrett and Benditt, Proc. Natl. Acad. Sci., 84, 1099-1103 (1987)) and also in activated human monocytes (Shimakado et al, Cell, 43, 277-285 (1985)) (Martinet et al, Nature, 319, 158-186 (1986)). Accurate quantitation of the various dimeric forms of PDGF may consequently serve as an indicator of pathological conditions. None of the current methods for quantitative assay of PDGF distinguish between the dimeric forms of the molecule and have therefore detected total levels of PDGF. Current methods for assay can be divided into 3 categories.
1) Bioassay based on the ability of PDGF to stimulate 3H thymidine incorporation into fibroblasts such as Swiss mouse 3T3 cells (Deuel et al, J. Biol. Chem., 256, 8896-8899 (1981)). (Kumar et al, FASEB J., 7, 2272-2277 (1988)).
2) Radioreceptor assays utilizing 1251 labelled PDGF as described by Singh et al, J. Cell. Biol., 95, 667-671 (1982), Bowen-Pope and Ross, In control of animal cell proliferation, eds. Boynton and Lefford, Vol. 1, 281-312 (1985); Nister et al, Cell, 52, 791-799 (1988); D. F. Bowen Pope, et al, J. Biological Chemistry Vol. 264, No. 5, pp. 2502-2508 (1989)
3) Enzyme immunoassay (Kumar et al, FASEB J., 7, 2272-2277 (1987)) (Martinet et al, New Engl. J. Med., 317, 202-209 (1988)).